Multiple-retort underfeed stoker



C. F. MILLER.

MULTIPLE RETORT UNDERFEED STOKER.

APPLICATION FILED SEPT. 19, I916.

Patented Sept. 14, 1920.

v INVENTOR.

BY {0426f HIS ATTORNEYJiN FACT,

' UNITED STATES PATENT OFFICE.

CHARLES I. MILLER, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO WESTING- HOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENN- SYLVANIA.

Specification of Letters Patent.

Patented Sept. 14, 1920.

Application filed September 19, 1916. Serial No. 120,977.

To all whom it may concern:

Be it known that I, CHARLES F. Mxnnnn, a citizen of the United States, and a resident of Pittsburgh in the county of Allegheny and State of liennsylvania, have made a new and useful Invention in Multiple- Retort Underfeed Stokers, of which the following is a specification.

This invention relates to underfeed stokers and has an object to produce a horizontal cry of blast to different portions of the fuel bed.

A further object is to produce a new and improved grate bar for horizontal underfeed stokers.

A further object is to produce a horizontal underfeed stoker which is of simple construction, is light in weight, has a high fuel burning capacity, and is more easily operated than other stokers of that type now in use and known to me.

These and other objects, which will be made apparent throughout the further description of my invention, are attained by means of apparatus empodying the features herein described and illustrated.

In the single sheet drawing accompanying and forming a part hereof, I have illustrated in transverse, vertical sectional elevation, a stoker embodying my invention.

In an application filed by me on the 19th day of September, 1916, and serially numbered 120,978, I have illustrated, described and claimed a horizontal underfeed stoker of the central ash discharge type. This stoker and the stoker illustrated inthe drawings forming a part hereof include two retors 4, each of which is located immediately adjacent to one side wall of the furnace and is adapted to feed fuel onto and over an ad jacent set of-stationary grate bars 5. As illustrated the grate bars of each set extend from their cooperatin retort toward the center of the furnace an a dump grate mechanism is located between the inner or adjacent ends of the grate bars of the two sets.

The grate bars of each set are shown inclined downwardly toward the center of the furnace although it will be apparent to those skilled in the art that they may be horizontally disposed without departing from the scope of the invention as it is set forth in the appended claims.

The grate bars 5 of each set are mounted on combined pedestal and spacing members 6, which also support the retorts 4.. The members 6 also form spacers for the air passages included in the stoker structure. As illustrated the space below each retort and its cooperating set of grate bars is divided into two chambers 7 and 8 by means of partition plates 9 mounted on the members 0. The former chamber may be termed the primary air chamber and receives air or blast under pressure from a duct or passage 10 located within the foundation of the stoker and communicating with the chamber 7 through a port 11, which may be controlled by a slide valve 13. The slide valve 11% may be actuated from the front of the stolcer as is customary.

In the stoker illustrated in the present application, blast is delivered from each primary air chamber through three separate passages or sets of passages. It is delivered to the retort twyers 14, to grate bar twyers 15, and to an air box 16, which forms a support for lower ends of the grate bars 5 of one set and delivers air to an interior passage of each grate bar supported an it.

As illustrated each grate bar of each set is supported at its inner end on one of the air boxes 16 and at its outer end on a support member 17. The mendwr 1? extends parallel to the adjacent retort 11. is mounted on the members 6, and is spaced from the inner wall of the adjacent retort by means of spacing pieces 18, which may be formed integrally with the members \Vith this arrangement. the inner wall of each retort and the adjacent support member 17 coop crate to form a blast passage which communicates directly with one chamber 7 and is adapted to deliver air or blast to a chamber or passage 19 formed in the retort end of each grate bar, and communicating with the twyer openings 15.

For this purpose the bar supporting face of each member 17 is provided with blast delivery ports, which are adapted to register with inlet ports 19 formed in the supported face of the ate bar and communicating with the c amber 19. As clearly illustrated in the drawing, each air box 16 is provided with a series of ports 16*, each of which is adapted to register with a port, formed in the air-box-supported end of a grate bar 5 and communicating with an air passage 20 of the grate bar. The passage 20 extends throu hout the major portion of the length of tlie grate bar and is separated from the passage 19 by means of a partition 21 which extends across the hollow interior of the bar. The air delivered to the passage 20 is discharged downwardly through a port 22 formed in the lower face of the grate bar and located immediately adjacent to the chamber 19. The air, delivered from the ports 22 of the grate bars 5 of each set, is received by one of the secondary air chambers 8 and is delivered, through openings between the bars 5, to the fuel bed or that portion of the fuel bed supported by the grate bars. With this method of deliverin air to the grate bars and to the fuel bed, t e grate bars are cooled and the greater portion of the air delivered to the fuel bed preheated, since it forms the cooling medium for the bars.

In this application, as in my application serially numbered 120,978, alternate grate bars 5 of each set reciprocate longitudinally on their supporting members,-but it will be understood that the ports, delivering air to the moving bars, are so proportioned that they will not throttle the air supply to the bars at any time during the motion of the bars. The moving grate bars 5 of each set are shown operatively connected to a rocker arm 30. which is located in the secondary air chamber below the grate bars, whereas the stationary bars are secured to the support members 16 and 17 in such a way as to prevent them from moving.

In order that the blast may be se arately controlled to different parts of the fiiel bed.

I have not only provided the two slide valves or dampers 13 for controlling the delivery of air into the primary air chambers, but I have also provided a damper 25 in each primary air chamber 7, which is capable of throttling down the air or blast delivered to the cooperating air box 16. As illustrated each damper 25 is located in the narrowest portion of one air chamber and between the inlet port 11 of that air chamber and the cooperating air box 16. The dampers 25 of course extend from the front to the rear of the furnace and are preferably controlled from the front of the furnace. lVith this arrangement the blast, delivered to that portion of the fuel bed located on the grate bars may be controlled without appreciably affecting the delivery of air issuing from the twyers 14 and 15. In the drawings I have also illustrated a valve 26 which is capable of delivering air from one of the chambers 7 to the ash pit. This valve may be controlled from the front of the furnace and consequently may be employed for adjusting the amount of air supplied through the twyer openings of a dump grate 27 which is pivotally mounted on one of the air boxes 16 and is adapted to swing downwardly for the purpose of dumping ash into the ash pit. \Vith this apparatus, the supply of air to the retort twyers 14 and 15, to the fuel bed on the grate bars, and to the ash pit or dump grate may be controlled.

The operation of the furnace is as follows: Fuel is delivered to each retort 4 by means of plungers or other apparatus which are adapted to continuously or periodically force fuel into, the retort at a point below the surface of the fuel maintained within the retort or maintained on the fuel supporting elements of the furnace. This method of feeding fuel to the retorts causes fuel to be crowded out of the mouth of each retort and onto the adjacent set of grate bars. The crowding action of the fuel together with the reciprocating motion of the moving grate bars causes the fuel to be distributed more or less uniformly over the grate bars and also over the dump grate 27 This distributing action is continuous or in other words fuel continuously moves from each retort toward the center of the furnace and the feed is so adjusted that the fuel will be practi cally consumed when it arrives at the center of the furnace. Blast is delivered to each of the ducts 10, which may be placed in communication with each other by means of a passage 28, and from each duct it is delivered to one of the primary air chambers 7 The blast is then distributed to the different passages, as has been previously described, and

that portion which passes through the grate bars is heated prior to being delivered to the fuel bed. The heating of the blast of course accomplishes a cooling of the grate bars and in addition to this the operating mechanism of the moving grate bars is also cooled by the passage of the air through the secondary air chambers 8. That portion of the blast which is delivered through the twyers 14 of each retort 4 is not preheated and consequentl it tends to keep the temperature down in that portion of the fuel bed located immediately adjacent to the side walls of the furnace. This together with the fact that the side walls are covered with green fuel, protects them from the intense heat generated within the combustion chamber of the furnace.

At the time of cleaning the furnace punch bars are introduced through openings located in the immediate vicinity of the dump grate 27 formed in the front and, if desired, in the rear of the furnace. That portion of the fuel bed located immediatel above the dump grate is then broken up or the purpose of breaking down any arching of the fuel bed which may occur across the dump grates, and also for the purpose of breaking up clinkers, which may have formed in the fuel bed, and of detaching them from the portions of the fuel bed located on the grate bars 5. After this is accomplished the grate 27, which in the stoker illustrated in the present application serves both sets of grate bars 5, is dropped and the ash and the clinkers supported by it fall into the ash pit. The grate is then raised and the fuel on the grate bars 5. is distributed over the dump grate for the purpose of protecting it from the intense heat of the combustion chamber. It will of course be understood that during the clearance operation the blast to the furnace is materially reduced or is shut down and that as soon as the dump grate is again raised the blast ma be delivered to the different arts of the urnace as desired.

While I have described but one embodiment of my invention, it will be apparent to those skilled in the art, that various changes, modifications, substitutions, additions, and omission ma be made in the apparatus illustrated wit iout departing from the spirit and scope of the invention as set forth by the appended claims.

What I claim is:

1. In an underfeed stoker two horizontal retors, a dump grate located between the retorts, a separate set of grate bars located between each retort and the dump grate, air supply means for each retort and cooperating set of grate bars, each means including a damper to control the flow of air both to the retort and the grate bars and a second damper to control the air flow to the grate bars, one of said means having a passageway adapted to afford communication to the space beneath the dump grate, and a damper for the passage-way.

2. An underfeed stokcr, comprising two retorts, an intermediate ash discharge mechanism, a separate set of grate bars between each retort and said mechanism, each grate bar of each set being provided with at least two air delivery ports and two air inlet ports, said air inlet ports being located at opposite ends of the bar, separate air boxes communicating with the inlet ports at the opposite ends of the grate bars of each set, a separate air chamber located below each set of grate bars and receiving air under pressure from one of the delivery ports of the rate bars thereabove, and separate means for controlling the delivery of air to each of said air chambers.

3. In an underfeed stokcr, a retort, a dump rate mechanism extending substantially arallel to the retort, a set of parallel grate ars extending transversely of the retort and between the retort and said mechanism, an air box on which the fuel discharge ends of the grate bars are mounted, and single piece pedestals extending transversely of the retort and on which said retort, said air box and said grate bars are mounted.

4. In an underfeed stokcr, a retort, a dump grate mechanism extending parallel to the retort, a set of parallel grate bars between the retort and said mechanism, a single-piece pedestal supporting said retort and grate bars, a partition means carried by said pedestal and dividing the space beneath the rate bars into primary and secondary air 0 ambers, means affording communication between the primary air chamber and the retort,and means for preheating and conducting air from the primary chamber to the secondary chamber.

5. In an underfeed stokcr, two retorts, an ash discharge mechanism located between the retorts, an air box between each retort and the ash discharge mechanism, a set of spaced grate bars extending from each retort to the ash discharge mechanism, the grate bars having air passages therein adapted to discharge into the air box, means for delivering .air under pressure to the fuel issuing from each retort, means for delivering air to the passages in the grate bars, means for controlling the sugply of air to the retort and to the grate ar passages, and means for controlling the supply of air to the grate bar passages independently of the first controlling means.

6. An underfeed stoker comprising two fuel feeding retorts, a central dump grate between the retorts, an air box between each retort and the dum grate, a separate set of grate bars located etween each retort and the dump grate, and above the air box, each set of bars including stationar 1 and moving bars, and each bar being provi ed with separate independent air passages, one formed within each end thereof, one of the said passages being adapted to receive air and discharge it into the fuel and the other of said passages being adapted to receive air and discharge it into the air box after it has become preheated. means for deliverin air to'the separate passages of the grate bars, and means for separately controlling the air delivered to at least one set of said passages.

In testimony whereof, I have hereunto subscribed my name this 18th day of September,

CHARLES F. MILLER. 

